Derivative Instruments and Hedging Activities - Schedule of Derivative Instruments (Details) - Not Designated as Hedging Instrument - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Derivative Asset [Abstract]
Notional Amount	$ 331,030	$ 139,337
Fair Value	5,886	1,916
Derivative Liability [Abstract]
Notional Amount	296,431	125,526
Fair Value	5,844	1,898
Customer derivatives – interest rate swaps
Derivative Asset [Abstract]
Notional Amount	295,566	124,627
Fair Value	5,843	1,895
Derivative Liability [Abstract]
Notional Amount	295,566	124,627
Fair Value	5,843	1,895
RPAs sold
Derivative Asset [Abstract]
Notional Amount	0	0
Fair Value	0	0
Derivative Liability [Abstract]
Notional Amount	865	899
Fair Value	1	3
RPAs purchased
Derivative Asset [Abstract]
Notional Amount	35,464	14,710
Fair Value	43	21
Derivative Liability [Abstract]
Notional Amount	0	0
Fair Value	$ 0	$ 0